Gift cards are raffled off between the counselors if you don't specify who they are to go to. This might even mean that some one from the "Lab" will get a gift card that you gave when your kid was in "Oceaneers". I think that this is ok, b/c a lot of parents of older kids don't bother to tip.
In Flounders, you can give the cards to each person individually, there are 4 full time counselors in there.
I agree that
Walmart cards would probably be more appreciated then the phone cards, when I spoke to one of the counselors at the end of our cruise, she said that a lot of the counselors have cell phones (like a previous poster mentioned), and that they do have a shuttle to Walmart for them.
We brought 10 $10 phone cards, and we have 2 kids, one used Oceaneers,and one Flounders. We gave 3 to flounders (b/c they only had 3 full timers on that week, one was on leave), and the other 7 to Oceaneers to be raffled.
BTW, any cash that is given, is put in a pot, and every several months (they alternate each group of counselors) one group will get a party at WDW or somewhere like that. It is not divided and given to individuals.